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Dock Homology Region 2, a GEF domain, of Class C Dedicator of Cytokinesis proteins DOCK proteins are atypical guanine nucleotide exchange factors (GEFs) that lack the conventional Dbl homology (DH) domain. As GEFs, they activate small GTPases by exchanging bound GDP for free GTP. They are divided into four classes (A-D) based on sequence similarity and domain architecture; class C, also called the Zizimin-related (Zir) subfamily, includes Dock6, 7 and 8. Class C DOCKs have been shown to have GEF activity for both Rac and Cdc42. Dock6 regulates neurite outgrowth. Dock7 plays a critical roles in the early stages of axon formation, neuronal polarity, and myelination. Dock8 regulates T and B cell numbers and functions, and plays essential roles in humoral immune responses and the proper formation of B cell immunological synapses. All DOCKs contain two homology domains: the DHR-1 (Dock homology region-1), also called CZH1 (CED-5, Dock180, and MBC-zizimin homology 1), and DHR-2 (also called CZH2 or Docker). The DHR-1 domain binds phosphatidylinositol-3,4,5-triphosphate. This alignment model represents the DHR-2 domain of Class C Docks, which contains the catalytic GEF activity for Rac and Cdc42. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",